import 'package:flutter_test/flutter_test.dart';
import 'package:patbond_flutter/core/models/patch_field.dart';

/// PATCH 三态的 JSON 表现（契约 v1.4.0 的 `UpdateMeRequest` /
/// `UpdatePetRequest.avatarAssetId`）。
///
/// 本文件守住的红线只有一条：**absent 绝不落键**。若 absent 落成 `null`，
/// 用户「只改昵称」会把头像一起清掉（服务端把显式 null 当清空指令）。
void main() {
  test('absent 不落键 / clear 落 null / value 落值', () {
    final json = <String, Object?>{};
    const PatchField<String>.absent().writeTo(json, 'a');
    expect(json.containsKey('a'), isFalse, reason: 'absent 必须连键都不出现');

    const PatchField<String>.clear().writeTo(json, 'b');
    expect(json.containsKey('b'), isTrue);
    expect(json['b'], isNull);

    const PatchField<String>.value('x').writeTo(json, 'c');
    expect(json['c'], 'x');
  });

  test('absent 与 clear 的 valueOrNull 同为 null，只能靠 isPresent 区分', () {
    const absent = PatchField<String>.absent();
    const clear = PatchField<String>.clear();
    expect(absent.valueOrNull, isNull);
    expect(clear.valueOrNull, isNull);
    expect(absent.isPresent, isFalse);
    expect(clear.isPresent, isTrue);
    expect(absent.isClear, isFalse);
    expect(clear.isClear, isTrue);
    expect(const PatchField<String>.value('x').isClear, isFalse);
  });

  test('encode 只作用于有值态（clear 不调 encode，避免 null 解引用）', () {
    final json = <String, Object?>{};
    var encodeCalls = 0;
    const PatchField<int>.clear().writeTo(
      json,
      'n',
      encode: (value) {
        encodeCalls += 1;
        return value.toString();
      },
    );
    expect(json['n'], isNull);
    expect(encodeCalls, 0);

    const PatchField<int>.value(7).writeTo(
      json,
      'm',
      encode: (value) {
        encodeCalls += 1;
        return value.toString();
      },
    );
    expect(json['m'], '7');
    expect(encodeCalls, 1);
  });

  test('值相等即相等（absent 与 clear 不相等）', () {
    expect(
      const PatchField<String>.value('a'),
      const PatchField<String>.value('a'),
    );
    expect(
      const PatchField<String>.absent(),
      isNot(const PatchField<String>.clear()),
    );
  });
}